Can anyone tell me what can be the reasons for blood coming from anal region during defecation?

Numerous: From hemorrhoids, fissures, fistulae, inflammatory bowel disease, diverticulosis, to polyps, tumors benign or malignant. Also meckel's diverticulum, and upper GI sources such as ulcers and gastritis and tumors benign or malignant. No bleeding is normal. Get properly evaluated by a GI doctor or colorectal surgeon or at least by your primary care doctor. Do not ignore rectal bleeding.